All questions of Air Pollution for Civil Engineering (CE) Exam

Isokinetic Sampling for SPM Sampling in Chimney Flue Gas

Isokinetic sampling is used for sampling of the flue gas in a chimney for SPM (Suspended Particulate Matter) measurement. It is a widely used method for the measurement of particulate matter emissions from stationary sources.

Working Principle:

The principle of isokinetic sampling is based on the concept of maintaining the velocity of the sampled gas constant. This is done to ensure that the particles in the sampled gas are captured accurately and representatively. The sampling rate is adjusted to match the velocity of the gas in the chimney, which is determined by measuring the gas velocity using a pitot tube or other velocity measurement device.

Procedure:

The isokinetic sampling procedure involves the following steps:

1. Determination of the gas velocity in the chimney using a pitot tube or other velocity measurement device.

2. Selection of the sampling location in the chimney based on the gas velocity.

3. Adjustment of the sampling rate to match the gas velocity.

4. Collection of the sample in a filter holder.

5. Weighing the filter before and after sampling to determine the concentration of SPM in the flue gas.

Advantages:

Isokinetic sampling has several advantages, including:

1. It ensures accurate and representative sampling of flue gas.

2. It is widely accepted and recognized as a standard method for particulate matter sampling.

3. It can be used for a wide range of particulate matter concentrations.

4. It is a cost-effective method for particulate matter measurement.

Conclusion:

Isokinetic sampling is a reliable and accurate method for sampling of the flue gas in a chimney for SPM measurement. It is widely used in the industry and is recognized as a standard method for particulate matter sampling.

Coning plume occurs under which conditions?
Coning plume occurs under sub adiabatic conditions.

Explanation:
A coning plume refers to the shape the plume takes as it rises from a source, such as a chimney or a stack. The shape is conical, with a wider base and narrower top. Coning plumes are commonly observed in industrial processes and can have significant environmental impacts.

Sub adiabatic conditions:
Under sub adiabatic conditions, the temperature of the surrounding air is lower than the temperature of the plume. This temperature difference causes the plume to rise and expand, resulting in a conical shape. The sub adiabatic condition occurs when there is heat loss from the plume to the surrounding air.

Other conditions:
Let's briefly discuss the other conditions mentioned in the question and why they are not correct:

- Super adiabatic conditions: Under super adiabatic conditions, the temperature of the surrounding air is higher than the temperature of the plume. In this case, the plume will not rise and expand, and therefore, a coning plume will not occur.

- Neutral conditions: Under neutral conditions, the temperature of the surrounding air is equal to the temperature of the plume. In this case, the plume will rise vertically without significant expansion, resulting in a columnar shape rather than a coning shape.

- Inversion conditions: Inversion refers to a situation where the temperature of the surrounding air increases with height. Under inversion conditions, the plume will be trapped beneath the inversion layer and will not rise vertically or expand, leading to a different plume shape rather than a coning shape.

Therefore, the correct condition for a coning plume to occur is sub adiabatic conditions, where the temperature of the surrounding air is lower than the temperature of the plume, causing the plume to rise and expand in a conical shape.

Activated alumina is used as a catalyst for removing hydrocarbons from gaseous pollutants in a combustion unit.

Activated Alumina as a Catalyst:
Activated alumina is a highly porous form of aluminum oxide that has a large surface area, high adsorption capacity, and excellent thermal stability. It is commonly used as a catalyst in various chemical processes, including the removal of hydrocarbons from gaseous pollutants.

Mechanism of Hydrocarbon Removal:
When hydrocarbons are present in gaseous pollutants, they can contribute to air pollution and pose a threat to human health and the environment. Therefore, it is essential to remove these hydrocarbons before releasing the gases into the atmosphere. Activated alumina acts as a catalyst to facilitate the conversion of hydrocarbons into carbon dioxide and water through the process of catalytic oxidation.

Adsorption:
Activated alumina has a high affinity for hydrocarbons and other volatile organic compounds (VOCs). The porous structure of activated alumina provides a large surface area, allowing for efficient adsorption of hydrocarbon molecules onto its surface.

Oxidation:
Once the hydrocarbon molecules are adsorbed onto the surface of activated alumina, oxidation reactions take place. The catalyst provides active sites where oxygen molecules can react with the adsorbed hydrocarbons, leading to their conversion into carbon dioxide (CO2) and water (H2O). This process is known as catalytic oxidation.

Regeneration:
Over time, the adsorption capacity of activated alumina may decrease as it becomes saturated with hydrocarbons. Therefore, periodic regeneration is required to restore its adsorption capacity. This can be achieved by heating the activated alumina at high temperatures, which removes the adsorbed hydrocarbons and allows the catalyst to be reused.

Advantages of Activated Alumina Catalyst:
- High adsorption capacity: Activated alumina has a large surface area, allowing for efficient adsorption of hydrocarbons.
- Thermal stability: The catalyst can withstand high temperatures without losing its effectiveness.
- Regenerability: Activated alumina can be regenerated, making it suitable for long-term use.
- Versatility: Activated alumina can be used for the removal of various pollutants, including hydrocarbons and VOCs.

In conclusion, activated alumina is an effective catalyst for removing hydrocarbons from gaseous pollutants in a combustion unit. Its high adsorption capacity, thermal stability, and regenerability make it a suitable choice for this application.

Reflection noise is the correct answer.

Explanation:
When sound waves hit a surface, they can be reflected, transmitted, or absorbed. Reflection noise occurs when sound waves bounce off surfaces and create echoes or reverberations in a space. This can result in an increase in overall noise levels and decrease speech intelligibility. Reflection noise can be particularly problematic in spaces with hard, smooth surfaces such as walls and ceilings.

How sound absorbing materials work:
Sound absorbing materials are designed to reduce reflection noise by absorbing sound waves rather than allowing them to bounce off surfaces. These materials are typically soft, porous, and lightweight, and they have the ability to convert sound energy into heat energy. When sound waves pass through these materials, they cause the fibers or particles in the material to vibrate, which in turn converts the sound energy into heat. This reduces the amount of sound that is reflected back into the space.

Benefits of lining walls and ceiling with sound absorbing materials:
By providing lining on walls and ceiling with sound absorbing materials, the following benefits can be achieved:

1. Reduced reflection noise: The primary benefit of using sound absorbing materials is the reduction of reflection noise. These materials help to absorb sound waves, preventing them from bouncing off surfaces and creating echoes or reverberations in the space. This can result in a quieter and more acoustically comfortable environment.

2. Improved speech intelligibility: Reflection noise can make it difficult to understand speech, especially in larger spaces such as conference rooms or auditoriums. By reducing reflection noise, sound absorbing materials can improve speech intelligibility and enhance communication.

3. Enhanced sound quality: Reflection noise can distort or muffle sound, affecting the overall quality of audio playback. By minimizing reflection noise, sound absorbing materials can improve the clarity and fidelity of sound reproduction.

4. Increased privacy: Reflection noise can also result in a lack of privacy, as sound can easily travel through walls and ceilings. By reducing reflection noise, sound absorbing materials can help create more private and confidential spaces.

5. Aesthetic appeal: In addition to their functional benefits, sound absorbing materials can also be visually appealing. They are available in a variety of colors, textures, and designs, allowing them to be integrated seamlessly into the overall design of a space.

Conclusion:
By providing lining on walls and ceiling with sound absorbing materials, reflection noise can be effectively abated. These materials absorb sound waves, reducing the amount of noise that is reflected back into the space. This can result in a quieter and more acoustically comfortable environment, with improved speech intelligibility, enhanced sound quality, increased privacy, and aesthetic appeal.

B) 10

c) 100

d) 1000

Sub Adiabatic Lapse Rate

When the environmental lapse rate (ELR) is less than the adiabatic lapse rate (ALR), a sub-adiabatic lapse rate occurs. This means that the temperature of the air decreases at a slower rate than the dry adiabatic lapse rate as it rises in the atmosphere.

Reason behind Sub Adiabatic Lapse Rate

This occurs because the air is not rising high enough or fast enough to cool at the dry adiabatic lapse rate through adiabatic cooling. Instead, the air is being cooled by other processes such as radiation or mixing with cooler air.

Effect of Sub Adiabatic Lapse Rate

A sub-adiabatic lapse rate can have a significant effect on weather patterns and atmospheric stability. It can lead to the formation of temperature inversions, where a layer of warm air is trapped below a layer of cooler air. This can lead to poor air quality and the accumulation of pollutants in the lower atmosphere.

Conclusion

In conclusion, when the environmental lapse rate (ELR) is less than the adiabatic lapse rate (ALR), a sub-adiabatic lapse rate occurs. This can have important implications for weather patterns and atmospheric stability.

Dynamic precipitator is used in ceramic industries.

Explanation:
Ceramic industries involve the production of ceramics, which are non-metallic solid materials that are typically made from clay and other raw materials. These industries often generate dust and other particulate matter during various processes such as grinding, crushing, milling, and drying. To control the emission of these particulates and ensure the production area remains clean, various air pollution control devices are employed.

One such device used in ceramic industries is the dynamic precipitator. Here is a detailed explanation of its working principle and advantages:

Working principle:
1. The dynamic precipitator is an electrostatic air cleaner that removes particles from the gas stream using the principle of electrostatic precipitation.
2. The gas stream containing particulates is passed through an ionization section, where corona discharge electrodes emit electrons that ionize the gas molecules.
3. The ionized gas molecules create a cloud of charged ions and electrons, which then interact with the particles in the gas stream.
4. The charged particles are attracted to oppositely charged collection electrodes, while the clean gas passes through.
5. The collected particles form a layer on the collection electrodes, and periodic rapping or shaking removes them, allowing continuous operation.

Advantages of dynamic precipitator:
1. High collection efficiency: Dynamic precipitators are highly efficient in removing particulates, even those with very small particle sizes.
2. Low pressure drop: These devices have a relatively low pressure drop, resulting in minimal energy consumption.
3. Continuous operation: The periodic rapping or shaking of collection electrodes allows continuous operation without frequent shutdowns for cleaning.
4. Versatile applications: Dynamic precipitators can handle a wide range of gas volumes and particulate concentrations, making them suitable for various ceramic industry processes.
5. Cost-effective: These devices offer long service life and require minimal maintenance, making them cost-effective solutions for air pollution control in ceramic industries.

In conclusion, the dynamic precipitator is used in ceramic industries to control particulate emissions and maintain a clean working environment. Its efficient particle collection, low pressure drop, continuous operation, and versatility make it a preferred choice for air pollution control in this industry.

Understanding Aerosols
Aerosols are tiny particles or droplets suspended in the air. They can be in different physical states, including solid and liquid. The distinction is important when classifying aerosols, as they have varying impacts on health, environment, and engineering applications.
Different Forms of Aerosols
- Fume: This is typically a solid aerosol, formed from the condensation of vaporized metals or other materials. Fumes are generally composed of very fine particles and are not considered liquid.
- Dust: Dust consists of solid particles that are often larger than those in fumes. It is primarily composed of soil, pollen, or other solid materials and does not fall under the liquid category.
- Mist: Mist is a liquid aerosol formed from tiny droplets of water suspended in the air. This is the correct answer as it represents a liquid form of aerosol. Mist can occur naturally (like fog) or be artificially generated (like in humidifiers).
- Smoke: Smoke is a complex mixture of gases and solid particles produced by the incomplete combustion of organic matter. While it contains liquid droplets, it is primarily classified as a solid aerosol due to its particulate nature.
Conclusion
In summary, among the options provided, mist is the only liquid form of aerosol. Understanding these classifications is crucial in various fields, including civil engineering, where aerosol behavior can affect air quality and material performance.

Incomplete burning of wood leads to the production of mainly carbon monoxide (CO) gas.

Explanation:

Incomplete combustion occurs when there is not enough oxygen present during the burning process. In the case of burning wood, incomplete combustion can occur if the fire is not hot enough, if there is not enough air flow, or if there is too much fuel and not enough oxygen. Incomplete combustion of wood releases a number of gases, including carbon monoxide (CO), carbon dioxide (CO2), water vapor (H2O), and other volatile organic compounds (VOCs).

Carbon monoxide (CO) is a toxic gas that is produced when there is not enough oxygen present during combustion. Carbon monoxide is odorless, colorless, and tasteless, making it difficult to detect. In high concentrations, carbon monoxide can be deadly. Carbon monoxide is produced when wood is burned incompletely because the carbon in the wood does not fully combine with oxygen to form carbon dioxide.

Conclusion:

In conclusion, incomplete burning of wood leads to the production of mainly carbon monoxide (CO) gas, which is a toxic gas that can be deadly in high concentrations. Therefore, it is important to ensure complete combustion of wood by providing enough air flow and maintaining a hot fire.

The primary air pollutant that is formed due to incomplete combustion of organic matter is carbon monoxide (CO). When organic matter such as fossil fuels (coal, oil, and natural gas) or biomass (wood, crops, and agricultural waste) is burned in an environment with insufficient oxygen supply, incomplete combustion occurs, leading to the formation of carbon monoxide.

Incomplete combustion happens when there is not enough oxygen available to fully react with the carbon in the fuel. Instead of producing carbon dioxide (CO2), which is the desired end product of complete combustion, carbon monoxide is formed. Carbon monoxide is a colorless and odorless gas that is highly toxic to humans and animals.

**Formation of Carbon Monoxide:**
During the process of incomplete combustion, the carbon in the organic matter combines with only one oxygen atom instead of two, forming carbon monoxide. The chemical equation for this reaction can be represented as:

C + O2 -> CO

In this equation, C represents carbon, O2 represents oxygen, and CO represents carbon monoxide.

**Sources of Incomplete Combustion:**
Incomplete combustion can occur in various sources, including:
1. Vehicles: Inadequate air supply in the engine can lead to incomplete combustion in vehicles, especially those with older or poorly maintained engines.
2. Industrial Processes: Certain industrial processes that involve the burning of fossil fuels or biomass may produce carbon monoxide if there is insufficient oxygen supply.
3. Residential Heating: Incomplete combustion can occur in households that use wood-burning stoves, fireplaces, or other heating appliances that do not provide enough oxygen for complete combustion.
4. Wildfires: During wildfires, the burning of vegetation can result in incomplete combustion and the release of carbon monoxide into the atmosphere.

**Health and Environmental Impacts:**
Carbon monoxide is a poisonous gas that can have severe health effects on humans and animals. When inhaled, it binds to hemoglobin in the blood, reducing its ability to transport oxygen throughout the body. This can lead to symptoms such as headaches, dizziness, nausea, confusion, and in severe cases, it can be fatal.

In addition to its health impacts, carbon monoxide is also an air pollutant that contributes to the formation of smog and can contribute to the greenhouse effect and climate change. It reacts with other pollutants in the atmosphere to form ground-level ozone, which is harmful to human health and the environment.

**Conclusion:**
The primary air pollutant formed due to incomplete combustion of organic matter is carbon monoxide. It is important to ensure proper combustion conditions and adequate oxygen supply to minimize the production of carbon monoxide and reduce its harmful impacts on human health and the environment.

And nitrogen oxides in the presence of sunlight. The hydrocarbons and nitrogen oxides (NOx) are emitted from vehicle exhaust and other sources. When they react in the presence of sunlight, a complex chain of chemical reactions occurs, leading to the formation of photochemical smog. This type of smog is characterized by a brownish haze, and can cause respiratory problems, eye irritation, and other health issues. To reduce photochemical smog, it is important to reduce emissions of hydrocarbons and NOx from vehicles and other sources, as well as to minimize exposure to sunlight during peak hours.